What is a coolant change or flush?

A coolant change involves simply draining the coolant at the bottom of the radiator, then topping up the radiator with fresh fluid until it it’s full. Alternatively, the technician can remove the drain plugs on the engine block, which lets all the coolant drain out of the engine and cooling system components, and then top up with new coolant.

A coolant flush is more complex, and usually a bit more expensive. Instead of letting gravity do the work, flushing uses water pressure to blast any accumulated contaminants out of the cooling system’s passageways. Both the radiator and the engine block are cleaned out. The final step is to add new replacement coolant.

Should I get a coolant change or coolant flush?

While some shops may always recommend a coolant flush, they usually aren't necessary — a regular drain-and-fill will work fine. Always springing for a coolant flush will cost you more money than you need to spend.

Here are a few simple guidelines for whether you should drain or flush your coolant when it needs servicing:

Check your owner’s manual or warranty booklet to see what the manufacturer recommends. Most will simply say to change the coolant, which usually means a drain and fill. If you have a pretty new car, or you’ve been punctual with your routine maintenance schedule, your car should be just fine with this.

However, if the manufacturer recommends flushing your cooling system at certain intervals, then definitely do it. Make sure that any instructions that the manufacturer specifies for this procedure are followed.

If you have an older, possibly neglected vehicle with a cooling system problem, a coolant flush is the best way to achieve this. This is particularly the case if your coolant has become contaminated with corrosion, rust or debris.

What symptoms may require a coolant flush?

Not changing the coolant in your vehicle on a regular basis may affect engine performance. So, it's important to have it serviced routinely as part of factory scheduled maintenance. If the coolant has not been flushed regularly, you may experience one of more of these symptoms:

Can I drive with a coolant problem?

If you have your coolant changed or flushed as part of your scheduled maintenance, you shouldn't have issues with your coolant. However, driving a vehicle with old coolant or a faulty cooling system can result in overheating, cylinder head gasket failure, engine block failure or cylinder head warping. It is never recommended to drive a vehicle with engine cooling issues, especially with modern engine casting materials.

How often should the coolant be changed or flushed?

On older vehicles, it's often recommended to flush the cooling system every two years or 30,000 miles. Many newer vehicles have extended-life coolant that can last up to 100,000 miles. It's always recommended to follow the service intervals in the owner's manual. Following the required services listed, whether it's a coolant change or coolant flush, will help ensure the longevity of the cooling system, as well as the rest of the vehicle.

Outside of routine maintenance, coolant may need to be drained and replaced when repairing a cooling system leak. In that case, a full coolant flush should be performed if excessive corrosion is present, or if the factory scheduled service interval has already been passed.

How does coolant work?

Coolant is a mixture of antifreeze and water. As it circulates, it absorbs the intense heat generated by the combustion process in your engine. The coolant then goes through your radiator, where it releases that heat. This is a continuous process that keeps your engine at an optimal operating temperature, for good fuel economy and smooth running.

Your coolant has other protective jobs to do as it circulates through your engine. Its high alcohol content protects against freezing at low temperatures and overheating at high temperatures. Additives blended into your coolant prevent corrosion, rust and mineral deposits from forming in your cooling system.

How is a coolant change or flush performed?

Changing the coolant, which is a separate activity from a coolant flush, is done by simply draining the coolant from the radiator, refilling the engine coolant through the reservoir, and running the vehicle until it is full and free of air.

A coolant flush is much the same, but differs in that there is normally a chemical treatment additive circulated through the engine before draining the coolant. The next step in a flush is to run water into the entire cooling system, flushing out the chemical treatment, corrosion and old engine coolant.

Then the radiator and engine block, if equipped with a drain plug, will be drained completely. Once drained, the coolant reservoir is cleaned thoroughly and replaced. Finally, the engine cooling system will be refilled and bled of air.

What to be aware of with coolant flush services

There are many brands and types of coolant and engine flushing chemicals available to consumers. Many manufacturers supply a proprietary type that is designed to protect the specific materials used in the construction of the engine cooling system. They may also indicate optional recommended brands. These recommendations should be followed to help ensure the longevity of the cooling system.

Can I change the coolant myself?

The average DIYer can maintain the engine cooling system without much trouble. However, diagnosing the system when problems arise can be a daunting task if you don't understand what each component does. Changing or flushing the engine cooling system is generally safe for the moderately experienced DIYer. If cooling system issues develop after the coolant is replaced, this repair should be handed to a certified technician.